It is common practice to extract fluid samples from pressurized pipelines or the like for analysis in the field or for off-site, laboratory analysis. This is especially true in the natural gas industry, where the monetary value of the gas is dependent on its compositional analysis. Likewise, the chemical and oil refining industries also have needs for extracting fluid samples from pressurized fluid sources.
Sampling and/or monitoring of the material may take various forms. Probes may be used to extract physical samples from the process gas, which may contain entrained liquid. In addition, real-time or time delayed monitoring via sensors or the like (for example, temperature, flow, liquid phase content, pH, etc) provides information on the process gas and its attributes. Corrosion coupons or other exposure indicators are likewise used to provide valuable data.
When collecting material samples for external use, as well as other operations, it may be necessary or desirable to separate liquids from the sample, or subject the material to other conditioning during the its retrieval such as, for example, pressure reduction, which may be desirable, especially in a sampling scenario involving a high pressure source.
For analytical applications including archiving, testing or the like, it may be important to avoid JT cooling to prevent condensation of vapor phase constituents. In such a case, stepped or otherwise controlled pressure reduction may be desirable to avoid adiabatic pressure drop, which may occur where to great a pressure drop is made in a single stage of pressure reduction. This should be avoided as too great a pressure drop in a single stage could result in JT cooling of the gas below its hydrocarbon dew point, resulting in sample gas composition distortion and potentially inaccurate data on the process gas stream.
Multi-stage, prior art pressure regulators can be bulky and typically are limited to two stages, and in the past, little or no consideration was given to minimizing the J-T cooling effect in third party systems.
Past modular sample conditioning systems employing two or more stages have been typically bulky and located external the fluid source, may be exposed to the elements and ambient temperature (unless insulated and/or heated or cooled to the temperature of the flow stream), and may require specialized on-site setup and calibration.
Current modular sample conditioning systems are comprised of individual sample conditioning components mounted a plate or base module near the analyzer. Examples of such systems include Parker's Intraflow system, Swagelok, and Circor Tech. These current modular sample conditioning systems are housed near the analyzer, typically in heated analyzer shelters.